diff --git a/defaults/main.yml b/defaults/main.yml
index 2c66906..a5698a8 100644
--- a/defaults/main.yml
+++ b/defaults/main.yml
@@ -2,7 +2,7 @@
 # for check_mk you should set at least
 opn_packages:
   - bash
-  - ipmitool
+  - freeipmi
   - libstatgrab
   - dmidecode
 
@@ -28,6 +28,10 @@ opn_check_mk_path: /usr/local/sbin/check_mk_agent
 opn_check_mk_lib_dir: /usr/local/lib/check_mk_agent
 opn_check_mk_port: 6556
 
+# patches for the checkmk agent to apply
+opn_check_mk_patches:
+  - check_mk_agent-freeipmi.p0  # https://github.com/Rosa-Luxemburgstiftung-Berlin/ansible-opnsense-checkmk/issues/24
+
 # list of plugins and local checks to install
 opn_check_mk_local_checks:
   - gateways_status.py
diff --git a/files/check_mk_agent-freeipmi.p0 b/files/check_mk_agent-freeipmi.p0
new file mode 100644
index 0000000..d18e87a
--- /dev/null
+++ b/files/check_mk_agent-freeipmi.p0
@@ -0,0 +1,26 @@
+--- check_mk_agent	2023-12-15 09:32:07.194344000 +0100
++++ /usr/local/sbin/check_mk_agent	2023-12-15 10:25:58.113316000 +0100
+@@ -497,6 +497,23 @@
+             sed -e 's/ *| */|/g' -e "s/ /_/g" -e 's/_*$//' -e 's/|/ /g' |
+             grep -v -E '^[^ ]+ na ' |
+             grep -v ' discrete '
++    elif inpath ipmi-sensors; then
++        echo '<<<ipmi_sensors>>>'
++        if ipmi-sensors --help | grep -q legacy-output; then
++            IPMI_FORMAT="--legacy-output"
++        else
++            IPMI_FORMAT=""
++        fi
++        if ipmi-sensors --help | grep -q " \-\-groups"; then
++            IPMI_GROUP_OPT="-g"
++        else
++            IPMI_GROUP_OPT="-t"
++        fi
++        for class in Temperature Power_Unit Fan; do
++            ipmi-sensors ${IPMI_FORMAT} --sdr-cache-directory /var/cache ${IPMI_GROUP_OPT} "${class}" | sed -e 's/ /_/g' -e 's/:_/ /g' -e 's@ \([^(]*\)_(\([^)]*\))@ \2_\1@'
++            # In case of a timeout immediately leave loop.
++            if [ $? = 255 ]; then break; fi
++        done
+     fi
+ 
+     # State of LSI MegaRAID controller via MegaCli.
diff --git a/tasks/main.yml b/tasks/main.yml
index 3fc3d17..af971c4 100644
--- a/tasks/main.yml
+++ b/tasks/main.yml
@@ -35,6 +35,15 @@
     - opn_install_check_mk
     - checkmk_hostname is not defined
 
+- name: apply patches
+  ansible.posix.patch:
+    src: "{{ item }}"
+    dest: "{{ opn_check_mk_path }}"
+    remote_src: false
+  with_items: "{{  opn_check_mk_patches | default([]) }}"
+  when:
+    - opn_install_check_mk
+
 - name: create lib dirs
   ansible.builtin.file:
     path: "{{ opn_check_mk_lib_dir }}/{{ item }}"